Coahuila is a coal-rich region, and as the AFP reports, the Zetas muscled in on that industry assured of the financial gains that would come with it. But coal is of particular significance to the Zetas beyond its monetary rewards; mining is free from the sticky consequence of prohibitive laws attached to other rackets like drug selling or sex trafficking.

The Zetas reportedly mine the coal through their own poorly-paid workers, or they buy it from small-time miners who are obliged to cooperate. The coal is then resold to a state-owned company, which is also suspected of being in cahoots with the Zetas, at a profit 30 times greater than the initial investment.

Estimates of the cartel’s profits from coal mining in Coahuila hover around $25 million a year.

Though some report the mining operation has been an open secret in the region for some time, the Zetas involvement wasn’t widely known outside of the country until October when during a press conference, the former Coahuila governor Humberto Moreira told reporters that a recently killed Zetas leader was running the coal mining industry before his death.

The drug cartel’s involvement in an industry rife with human and environmental abuse lends itself to some obvious concerns. Al-Jazeera reports that the Coahuila mines are already noteworthy for being particularly unsafe, including one accident in 2006 where 65 people died. But tunnel collapses occur with some frequency there, as do methane gas explosions. Mexican human rights officials report that since the Zetas’ infiltration, miners are no longer allowed to utilize what little safety protocols they previously had access to, making the environment all the more hazardous.

But as Moreira explained for workers, it’s not a matter of choice, “Here those in poverty are forced to seek work where they can…”